What does the phrase "an old dog becomes a good dog" mean?

There is an old saying in the countryside called "an old dog becomes fine", which also has many meanings. For example, it means a dog that has been kept for a long time. It can understand people's words, watch gestures and do unbelievable things, so it is said that the old dog has become refined.

Once when I came home from farm work, I was thirsty and wanted to boil water to drink. The pot was full of water. I want to get some wood from a shed in the yard. My dog has no hitch and keeps barking at me. I yelled at him, but I didn't care and went to get the wood. Then the dog came up and bit my trouser leg. I don't think something is right. I stood in front of the shed and saw a snake in the woodpile. I knocked it off with a shovel and killed it. The dog kept barking at the snake. I was very moved at that time. This dog knows human nature.

Later, when I moved, my old dog died, and I raised another dog called Jucai. Because after moving, customers can't find a place. They came to my house downstairs and shouted "gather money, gather money", and the dog took people home. He is more famous than me, knows less about me, and knows more about gathering money.

Although it is only a saying, and some even a legend, people who have owned dogs have experienced too many such things. People who haven't owned a dog may think I'm talking nonsense, but people who have owned a dog, especially those who have kept it for a long time, have more amazing things happened. Let me tell you a story about my friend.

He has a dog at home. He lived in a bungalow at that time. As long as someone passes by, the dog barks at the bungalow, no matter how far it is. But one day, the police came to my neighbor's house to arrest people, and the dog stood on the bungalow and watched, but stopped barking. The friend said: animals are very sensitive, and they can't disturb the inner door.

I have lived in the countryside for a long time and raised several dogs. Every time a dog is taken away or stolen, it will be very sad. Although it is only an animal, dogs with humanity are really popular. My son has a pet dog. He is so stupid that he doesn't know how to describe it. The dog I used to have is gone. This is the gap, right?